Japanese unexamined patent application publication No. JP-A-H08-262957(Hereinafter, Patent document 1) describes a related art image forming apparatus. In the related art image forming apparatus, process cartridges are made to be detachably mounted in an apparatus main body.
In an image forming apparatus of this type, cartridge mounting guide members are provided on both left- and right-hand sides of a cartridge mounting space defined within the apparatus main body in such a manner as to confront each other. The process cartridge includes a photosensitive drum. In addition, bosses are formed on the process cartridge in such a manner as to project from both side surfaces in a rotational axis direction of the photosensitive drum. By the process cartridge being inserted into the apparatus main body while the bosses are being guided by the cartridge mounting guide members, the mounting of the process cartridge in the apparatus main body is attained.
In addition, a cartridge side coupling is provided on one of both the side surfaces of the process cartridge. This cartridge side coupling is disposed in an inside of a cylindrical portion which projects from the one side surface of the process cartridge. When the process cartridge is mounted in the apparatus main body, a main body side coupling which is provided on the apparatus main body is connected to the cartridge side coupling, so that a driving force is transmitted from the main body side coupling to the cartridge side coupling. The photosensitive drum is driven to rotate by the driving force so transmitted.